accuracy of a narrow band a/f gauge
05-17-2014 | 02:00 PM
#1
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TECH Apprentice
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From: kansas city,mo
accuracy of a narrow band a/f gauge hey guys i got a dynotune narrow band a/f gauge that reads mv and has a numeric display. just curious how close they was on getting accurate readings under wide open throttle.
05-17-2014 | 04:10 PM
#2
narrowbands are great around stoich that's why cars come with narrowbands usually to keep accurate fueling at cruise rpm to meet emmisions and corporate average fuel economy (cafe).
The problem lies when you go WOT or any time you enter PE (power enrichment) stock cars are programmed to come out of closed loop where the narrowband data supplies the information needed for proper fueling and instead goes into open loop where the narrowbands are ignored and fueling is based on preset tables in the pcm that were modeled with guess what ??? widebands during R&D so the OEM's will only use wideband data to set coded fueling.
As soon as you expose a narrowband to exhaust lower than around 14.0 to 1 it is at the far reaches of the "narrow band" that it is engineered to be able to read accurately , below that it is reporting full rich because it is as rich as it is designed to recognize. Problem is 14.0 is pretty damn lean for a normally aspirated engine which generally will end up somewhere between 12.5-13.0 to 1 depending on who is tuning it and whether they are out for every hp or to play it safe. Forced induction where your looking for somewhere in the 11.3-11.8 to 1 range typically 14 to 1 is catastrophically lean while a narrowband is reporting full rich see the problem ?
A wideband can read well beyond any afr you would need to run a gasoline engine on in any situation from pig rich 10 to 1 up to lean cruise 17 to 1.
Sell the narrowband on craigs list and pick up a wideband instead , they start around $200
The problem lies when you go WOT or any time you enter PE (power enrichment) stock cars are programmed to come out of closed loop where the narrowband data supplies the information needed for proper fueling and instead goes into open loop where the narrowbands are ignored and fueling is based on preset tables in the pcm that were modeled with guess what ??? widebands during R&D so the OEM's will only use wideband data to set coded fueling.
As soon as you expose a narrowband to exhaust lower than around 14.0 to 1 it is at the far reaches of the "narrow band" that it is engineered to be able to read accurately , below that it is reporting full rich because it is as rich as it is designed to recognize. Problem is 14.0 is pretty damn lean for a normally aspirated engine which generally will end up somewhere between 12.5-13.0 to 1 depending on who is tuning it and whether they are out for every hp or to play it safe. Forced induction where your looking for somewhere in the 11.3-11.8 to 1 range typically 14 to 1 is catastrophically lean while a narrowband is reporting full rich see the problem ?
A wideband can read well beyond any afr you would need to run a gasoline engine on in any situation from pig rich 10 to 1 up to lean cruise 17 to 1.
Sell the narrowband on craigs list and pick up a wideband instead , they start around $200
05-17-2014 | 09:00 PM
#3
Away from stoich, the sensor responds more to gas
temperature than mixture. Which makes it more of
an entertainment gizmo than a useful monitor.
In this chart you can see that, depending on temp,
850mV could be anywhere from 10:1 to 15:1. Now
that's useful.
This is why WBO2s control sensor temperature as the
first order of business. NBO2, nobody knows nuthin'.
temperature than mixture. Which makes it more of
an entertainment gizmo than a useful monitor.
In this chart you can see that, depending on temp,
850mV could be anywhere from 10:1 to 15:1. Now
that's useful.
This is why WBO2s control sensor temperature as the
first order of business. NBO2, nobody knows nuthin'.